In post-war Germany, Wilson, an American delegate to the Allied War Crimes Commission, demands that Nazi prisoner of war Meinike be allowed to escape so that he may lead the Commission to his former boss, Franz Kindler, the most dangerous and elusive Nazi of all. Watched carefully by Wilson, the freed Meinike travels to Latin America and there contacts a former Nazi cohort about the whereabouts of Kindler. After some resistance, Meinike learns that Kindler, an avowed clock enthusiast, is living under the name Professor Charles Rankin in a small Vermont town called Harper. As soon as Meinike arrives in Harper, which boasts an old, ornate church clock, he deposits his suitcase at the local drugstore and heads for the school at which Rankin is a teacher. At the school, Meinike becomes aware that he is being followed by Wilson and knocks him unconscious in the gymnasium. Fleeing, Meinike goes to Rankin's home, where he meets the unsuspecting Mary Longstreet and learns that she and Rankin are to be married that evening. After Meinike finally locates Rankin near the school, a nervous, tense Rankin orders him to the woods. There, Rankin informs Meinike that he is marrying Mary, the daughter of a Supreme Court Justice, only because she is the perfect cover for him. When Meinike, who claims to have found God, reveals that he was followed to Harper, Rankin chokes him to death and buries him under a pile of leaves. Wilson, meanwhile, revives and, as Mary and Rankin are being married, heads for the drugstore, where owner Mr. Potter tells him about the mysterious Meinike and his suitcase. Wilson soon narrows his list of suspects to Rankin, who has been fixing the church clock, then poses as an antique dealer and clock enthusiast in order to ingratiate himself to Mary and the professor. While dining with Wilson, Mary, her brother Noah and her father, Rankin speaks disparagingly about Germany and convinces Wilson of his innocence. Later that night, however, Wilson remembers that Rankin had said that Karl Marx was not a "German" because he was a Jew, and decides to continue his investigation. At the same time, Rankin goes to check up on Meinike's body in the woods and is upset when Red, Mary's dog, begins to dig at the site. The next day, Wilson goes fishing with Noah and, sensing that the teenager dislikes Rankin, asks him to help in his investigation. After Noah agrees to find out everything that Mary did on her wedding day, Wilson and Potter open Meinike's suitcase in the drugstore. Although the suitcase's contents reveal nothing, Wilson uses it as a pretext to question Mary, who comes in with Rankin, about Meinike. When Mary starts to mention that she had met the strange man, Rankin silences her. Later, Rankin "confesses" to Mary that Meinike was blackmailing him about an accidental death in which he was involved, and Mary believes him when he claims that he paid the foreigner off. When Noah discovers Red dead from poison, Wilson deduces that he was killed by Rankin because he was digging at Meinike's grave, and a search is instigated. Realizing that his crime is about to be discovered, Rankin tells Mary that he had to kill the blackmailing Meinike to protect her from scandal. Still confident of her husband's goodness, Mary insists on escaping with him, even as Meinike's body is being uncovered by the townspeople. Wilson, however, is determined that she should know the truth about Rankin and has her father call her to his home. Although Mary insists on Rankin's innocence, Wilson is sure that she understands the situation on a subconscious level and suspects that Rankin will attempt to kill her. As predicted, Mary begins to unravel emotionally, and Rankin plots to murder her by sawing a step in the church tower ladder and ordering her to meet him there alone. Sara, Mary's devoted housekeeper, however, feigns a heart attack in order to prevent Mary from going, and Mary asks Noah to notify Rankin that she is going to be late. While Rankin plays checkers with Potter, Noah and Wilson go to the church. After Noah is nearly killed by the sabotaged step, Rankin returns home and is startled to see Mary there. Distraught, Rankin reveals his scheme to a horrified Mary, who, sure that she has caused Noah's death, orders her husband to kill her. Rankin, however, cannot do the deed and flees to the church tower. Later that night, Mary finds an armed Rankin and declares her intention to kill him. At that moment, however, Wilson shows up, and a struggle ensues. Mary retrieves Rankin's gun and shoots him in the shoulder, after which Rankin stumbles onto the clock face and is skewered by one of the clock's lance-wielding statues. As a mob of angry townspeople watch, Rankin falls to his death, and Mary is finally freed from his past.